X-ray tube target for reduced off-focal radiation

Abstract

An X-ray tube comprises an anode assembly having an associated anode and a cathode assembly for providing a focused electron beam directed to the anode. An anode target, associated with the anode assembly, accelerates the electron beam and produces X-rays upon electron impact with the anode target. Off-focal radiation tends to be most intensely emitted by the top surface of the target. In conventional X-ray tubes, the off-focal radiation as seen by the detector encompasses almost the entire top surface of the target assembly. In accordance with the present invention, the anode target comprises a cut-out top surface for reducing off-focal radiation, by blocking the off-focal radiation from the top surface from reaching the detector. Blocking the radiation produced at the top surface becomes more important as the ratio of the track area visible at the detector decreases with respect to the top surface area.

We claim: 
     
       1. A method for modifying an anode target of an X-ray tube to reduce off-focal radiation produced by the anode target and seen by an associated detector situated along a line of sight of a top surface of the anode target, the method comprising the steps of: providing an anode target, the top surface of the anode target capable of emitting off-focal radiation, the off-focal radiation detectable by the detector; and   modifying the anode target by removing a section of the top surface to create a cut-out depth in the top surface, whereby the cut-out depth blocks the off-focal radiation from the anode target top surface from reaching the detector.   
     
     
       2. A method as claimed in claim 1 wherein the step of modifying the anode target by removing a section of the top surface further comprises the step of forming a cut-out depth in the top surface, the cut-out depth having squared edges. 
     
     
       3. A method as claimed in claim 1 further comprising the step of notching the existing top surface of the anode target to form the cut-out depth. 
     
     
       4. A method as claimed in claim 1 wherein the step of modifying the anode target by removing a section of the top surface further comprises the step of forming a cut-out depth in the top surface, the cut-out depth having a concave configuration. 
     
     
       5. A method for reducing off-focal radiation in an X-ray tube, the method comprising the steps of: providing an anode assembly;   providing a standard anode target associated with the anode assembly, the anode target having a top surface;   situating a detector along a line of sight of the top surface of the anode target;   generating x-rays in a focused electron beam, the x-rays being produced upon impact of the focused electron beam with the anode target, the focused electron beam also producing scatter of electrons that can cause off-focal radiation to be seen by the detector along the line of sight of the anode target top surface; and   reducing the off-focal radiation seen by the detector by forming a cut-out depth in the anode target top surface to block the off-focal radiation from reaching the detector.   
     
     
       6. A method as claimed in claim 5 further comprising the step of notching the existing top surface of the anode target to form the cut-out depth. 
     
     
       7. A method as claimed in claim 5 wherein the step of reducing the off-focal radiation seen by the detector by forming a cut-out depth further comprises the step of forming a cut-out depth having squared edges. 
     
     
       8. A method as claimed in claim 5 further comprising the step of improving flatness of an umbra region of the electron beam. 
     
     
       9. A method as claimed in claim 5 wherein the step of reducing the off-focal radiation seen by the detector by forming a cut-out depth further comprises the step of forming the cut-out to have a depth sufficient to hide the line of sight of the top surface of the target from the detector. 
     
     
       10. A method as claimed in claim 5 wherein the anode target top surface emits off-focal radiation.